Thanks for the replies, the exercise I was doing was a bit like this (except I was alternating arms with each rep) Forearm Plank Rotation - YouTube I was really protracting my shoulders in order to hit my serratus hard
The pain has calmed down a bit now although is still feeling pretty sure around my back… although it feels more like it’s under my shoulder blade, wouldn’t say it feels like my back muscles exactly
I’ve also been doing a lot of exercises for my rotator cuffs and lower traps